Some law enforcement agencies are trying to avoid letting the public know what they’re doing. The law enforcement guide for police in Irvine, Calif., specifically states, “Do not disclose this information in court any more than is absolutely necessary to make your case. Never disclose to the media these techniques—especially cell tower tracking.” We saw the same attitude in training materials from the Iowa Fusion Center, which instructs law enforcement, “Do not mention to the public or media the use of cell phone technology or equipment to locate the targeted subject.” Read: “We would hate for the public to know how easy it is for us to obtain their personal information. It would be inconvenient if they asked for privacy protections.” Law enforcement could most likely solve more crimes more expediently if they could break down a suspect’s front door or open his/her postal mail without a warrant, but as my colleague Catherine Crump points out, while that may be convenient, it is not okay. Warrantless cell phone location tracking shouldn’t be either.

Fortunately, Irvine’s isn’t the only word on advice to law enforcement agents. Santa Ana, Calif., provides its agents with much more civil liberties-friendly training than its neighbor to the south, and its warnings should serve any law enforcement agency: “Without a warrant . . . cell phone location data are released only in exigent situations. Exigent circumstances are best described as immediate danger of death or serious bodily injury to any person. Keep in mind that even if you convince a provider that the circumstances warrant release of the information, a district attorney and defense attorney will at some point be reviewing the case.”

More importantly, some of the law enforcement agencies in California, Nevada, North Carolina, and Wisconsin, reported that, like their counterparts in parts of Hawaii, Kansas, Kentucky, Nevada, and New Jersey, they always obtain probable cause warrants in order to track cell phone location information. And then there’s the Hawaii Department of Land and Natural Resources, which does not currently track cell phone location information, but which promised that if it starts sometime in the future, it will definitely require probable cause warrants in order to do so. We hope other law enforcement agencies will make similar commitments. Location information is too sensitive for law enforcement agencies to be accessing it in criminal investigations without a warrant, and these agencies show that in every geographic region in the country, a warrant requirement is a completely reasonable and workable policy. And by the way, the law enforcement agency in Nevada that reports obtaining warrants? Las Vegas Metropolitan Police Department. If Sin City police get warrants, can’t everyone?

The new documents also touch on one of the most common questions we’ve been asked about cell phone location tracking: in what sorts of investigations are law enforcement agencies using cell phone location tracking? It’s a question that 5,509 pages later we still wish we had a better answer to and that, despite our records requests, the public is still largely in the dark about. San Bernadino County, Calif., sent us a ton of invoices from a one year period. (Any number-crunchers out there want to figure out how much money they spent to track cell phones that year? The documents are here.) “Okay to pay narcotics” was scrawled on some of the invoices. Others were marked “Okay to pay [redacted].” From this, we can surmise that cell phone location tracking is used in drug cases (no surprise to anyone who has been following the few location tracking cases to make it to the courts). Either they redacted “narcotics” on some invoices and not others, or they redacted other types of investigations where cell phone tracking was used, and someone out there does not want us to know what all they’re using cell phone location tracking for.